G4S bosses have insisted the company will be claiming tens of millions of pounds in management fees despite being 100% responsible for a "humiliating shambles".

Nick Buckles, chief executive of the world's second largest private sector employer, admitted he was sorry and "deeply disappointed" after the firm failed to deliver on its £284 million Olympics security contract.

But he repeatedly insisted the firm still intended to claim its £57 million management fee for work over the last two years, even though it cannot provide the guards needed for the Games.

Keith Vaz, chairman of the Commons Home Affairs Select Committee, said it was "astonishing" and called on G4S to waive the fee and any others associated with the contract.

Mr Buckles is under pressure to quit his £830,000-a-year job over the fiasco, which has resulted in the emergency deployment of soldiers, marines, airmen and police officers and seen £400 million wiped off the market value of G4S. He admitted he could not deny that the debacle was a "humiliating shambles for the company" and the firm's reputation was now in tatters.

Tory MP Nicola Blackwood said Mr Buckles's performance before the MPs "would lead quite a lot of people to despair". She added: "I had very little confidence in G4S fulfilling this contract before this session started and now I don't have any confidence at all."

Labour MP Bridget Phillipson told Mr Buckles she was left with the feeling that he was "making it up as you go along". Tory MP Michael Ellis added that the public was "sick of huge corporations like yours thinking they can get away with everything".

Mr Buckles promised the firm would pay all police and military costs caused by G4S's failure, would cover any accommodation expenses and would even consider paying bonuses to individual officers and troops if considered appropriate. But asked by Mr Vaz why the firm still wanted to claim its management fee, Mr Buckles said: "We've managed the contract and we've had management on the ground for two years. We still expect to deliver a significant number of staff."

Meanwhile, G4S has come under more fire after retired police officers claimed they were told they are no longer needed to help with security at the Olympics because they are "surplus to requirements". A representative of the National Association of Retired Police Officers claimed just days after he was sent an email offering employment at the Games for retired officers, he was sent another from the private security firm saying further recruitment was "surplus to requirements" because of the deployment of military and extra police resources.

But G4S said the letter was sent about a week ago at a time when it had been refused dispensation to use former police officers who had not completed necessary training and accreditation, and they were not "surplus to requirements" but lacked necessary accreditation and cannot be employed at London 2012.